Transversely expandable minimally invasive intervertebral cage

ABSTRACT

Disclosed herein are systems and methods for intervertebral body fusion that provide more robust support within the disc space. Intervertebral body fusion devices can have a unitary monolithic body including a plurality of body segments interconnected with each other by flexure members. Devices be configured to be inserted through an opening in a compressed configuration and then expanded within the disc space to an expanded configuration. In the expanded configuration, devices can have a greater mediolateral or transverse to the disc space footprint. This wider footprint provides greater support for the vertebrae relative to the size of the opening through which the device is inserted.

TECHNICAL FIELD

The present invention relates to the fusion of vertebral bodies. Morespecifically, the present invention relates to devices and associatedmethods for fusion of vertebral bodies that provide robust spinalsupport in a less invasive manner.

BACKGROUND

The concept of intervertebral fusion for the cervical and lumbar spinefollowing a discectomy was generally introduced in the 1960s. Itinvolved coring out a bone graft from the hip and implanting the graftinto the disc space. The disc space was prepared by coring out the spaceto match the implant. The advantages of this concept were that itprovided a large surface area of bone to bone contact and placed thegraft, under loading forces that allowed osteoconduction and inductionenhancing bone fusion. However, the technique is seldom practiced todaydue to numerous disadvantages including lengthy operation time,destruction of a large portion of the disc space, high risk of nerveinjury, and hip pain after harvesting the bone graft.

Presently, at least two devices are commonly used to perform theintervertebral portion of an intervertebral body fusion: the first isthe distraction device and the second is the intervertebral body fusiondevice, often referred to as a cage. Cages can be implanted asstandalone devices or as part of a circumferential fusion approach withpedicle screws and rods. The concept is to introduce a distractiondevice that will distract a collapsed disc in a generally axialdirection, decompress the nerve root, and allow load sharing to enhancebone formation, and then implant an intervertebral fusion device that issmall enough to allow implantation with minimal retraction and pullingon nerves.

In a typical intervertebral body fusion procedure, a portion of theintervertebral disc is first removed from between the vertebral bodies.This can be done through either a direct open approach or a minimallyinvasive approach. Disc shavers, pituitary rongeours, curettes, and/ordisc scrapers can be used to remove the nucleus and a portion of eitherthe anterior or posterior annulus to allow implantation and access tothe inner disc space. The distraction device is inserted into thecleared space to enlarge the disc space such that the vertebral bodiesare separated in a generally axial direction by actuating thedistraction device. Enlarging the disc space is important because italso opens the foramen where the nerve root exists. It is important thatduring the distraction process one does not over-distract the facetjoints. An intervertebral fusion device is next inserted into thedistracted space and bone growth factor, such as autograft, a collagensponge with bone morphogenetic protein, or other bone enhancingsubstance may be inserted into the space within the intervertebralfusion device to promote the fusion of the vertebral bodies.

Intervertebral distraction and fusion can be performed through anterior,posted or, oblique, and lateral approaches. Each approach has its ownanatomical challenges, but the general concept is to fuse adjacentvertebra in the cervical thoracic or lumbar spine. Devices have beenmade from various materials. Such materials include cadaveric cancellousbone, carbon fiber, titanium and polyetheretherketone (PEEK). Deviceshave also been made into different shapes such as a bean shape, footballshape, banana shape, wedge shape and a threaded cylindrical cage.

As with all minimally invasive surgeries, a primary goal is to provideequivalent or near equivalent treatment as more invasive surgicaltechniques but with less discomfort, recovery time, etc. for thepatient. One problem with minimally invasive intervertebral fusionprocedures is that the limited size of the surgical access limits thesize of the implant(s) that can be inserted. While devices that arevertically expandable in a generally axial direction have addressed someof these issues by being able to be inserted through a smaller openingand then made taller in a generally axial direction within the discspace, such devices are still limited in the transverse footprint thatcan be covered within the disc space which can affect the stability ofthe device within the disc space and limits the area for bone grown.

SUMMARY

Disclosed herein are systems and methods for intervertebral body fusionthat provide more robust support within the disc space. Intervertebralbody fusion devices can have a unitary monolithic body including aplurality of body segments interconnected with each other by flexuremembers. Devices be configured to be inserted through an opening in acompressed configuration and then expanded within the disc space to anexpanded configuration. In the expanded configuration, devices can havea greater mediolateral or transverse to the disc space footprint. Thiswider footprint provides greater support for the vertebrae relative tothe size of the opening through which the device is inserted.

In one embodiment, an expandable intervertebral body fusion deviceincludes a unitary monolithic body having a plurality of body segmentsconnected to each other with flexure members and an opening definedbetween the plurality of body segments. The device body can include ananterior body segment, a posterior body segment and one or moremediolateral body segments extending between the anterior body segmentand the posterior body segment along both a lateral side and a medialside of the anterior body segment and the posterior body segment. Athreaded opening can be formed in one or more of the anterior bodysegment and the posterior body segment. The body is configured to bemediolaterally expanded from a compressed configuration to an expandedconfiguration by interaction of an expansion tool with the threadedopening causing the one or more mediolateral body segments on thelateral side and the one or more mediolateral body segments on themedial side to generally move away from each other and expand theopening between the plurality of body segments such that the body formsa greater mediolateral footprint in the expanded configuration than inthe compressed configuration.

In one embodiment, a transversely expandable intervertebral body fusiondevice for a disc space between adjacent vertebra of a spine of a humanpatient includes a unitary monolithic body configured in size and shapeto be implantable in the disc space. The body can have at least fourbody segments each connected to adjacent body segments by one or moreflexure members with the body segments surrounding and collectivelydefining an opening within a transverse plane bisecting the body. Thebody segments can include an anterior body segment, a posterior bodysegment and at least one mediolateral body segment extending between theanterior body segment and the posterior body segment along each of alateral side and a medial side of the body. A threaded opening can beformed in at least one of the anterior body segment and the posteriorbody segment. The body can be configured to be mediolaterally expandedfrom a transversely compressed configuration to a transversely expandedconfiguration by interaction of an expansion tool with the threadedopening causing the at least one mediolateral body segments on each sideto generally move transversely away from each other, thereby expandingthe opening of the body and forming a perimeter defined by an outer edgeof the body that presents a mediolateral footprint in the expandedconfiguration that is greater than in the compressed configuration.

The above summary is not intended to describe each illustratedembodiment or every implementation of the subject matter hereof. Thefigures and the detailed description that follow more particularlyexemplify various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter hereof may be more completely understood in considerationof the following detailed description of various embodiments inconnection with the accompanying figures, in which:

FIGS. 1A-1D depict an expandable intervertebral body fusion device in acollapsed configuration according to an embodiment.

FIGS. 2A-2D depict the expandable intervertebral body fusion device ofFIGS. 1A-1D in an expanded configuration.

FIGS. 3A-3C depict a portion of the expandable intervertebral bodyfusion device of FIGS. 2A-2D.

FIG. 4 depicts a schematic representation of an expandableintervertebral body fusion device according to an embodiment beinginserted between vertebrae of a patient.

FIGS. 5A-5B depict a schematic representation of an expandableintervertebral body fusion device according to an embodiment insertedbetween vertebrae of a patient in a compressed and an expandedconfiguration.

FIGS. 6A-6B depict an expandable intervertebral body fusion device and acorresponding insertion device according to an embodiment.

FIGS. 7A-7F depict portions of an insertion device for an expandableintervertebral body fusion device according to an embodiment.

FIGS. 8A-8C depict portions of an insertion device for an expandableintervertebral body fusion device according to an embodiment.

FIGS. 9A-91 depict portions of an insertion device and an expandableintervertebral body fusion device according to an embodiment

While various embodiments are amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the claimedinventions to the particular embodiments described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the subject matter as defined bythe claims.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D and 2A-2D depict an expandable intervertebral body fusiondevice 100 according to an embodiment. FIGS. 1A-1D depict the device 100in a collapsed configuration and FIGS. 2A-2D depict the device 100 in anexpanded configuration. In practice, the device 100 is inserted into thedisc space through a minimally invasive access in the collapsedconfiguration and then expanded inside of the disc space. Inembodiments, the device 100 is inserted between adjacent vertebrae 10 onits side as depicted in FIG. 4 such that when it is expanded in the discspace rather than expanding vertically it expandshorizontally/transversely to the disc space to enable the device to takeup a larger footprint within the disc space as can be seen contrastingFIG. 5A and FIG. 5B. The device is therefore able to occupy more lateralto medial and anterior to posterior space within the disc space relativeto the size of the access that has heretofore been possible. In oneembodiment in its insertion and un-expanded state the device is 8 mm inheight, 11.5 mm in width and 26 mm in length. The device can have manyheights from 8 mm up to 16 mm. In embodiments, the width can go from8-12 mm and the length from 22 mm-32 mm. When the device is expanded,the height remains the same but the width can double or nearly double(from 11.5 to 22 mm or 47%) and the length goes from 26 mm to 20 mm (16%decrease). The device can have many lordotic angles from 0 to 15 degreesor higher; the most common being 0, 6, 12 degrees. The horizontal topand bottom of the device can have different shapes to better fit theendplates such as football shaped or domed. Also, the different segmentsof the device separated by flexures could be tailored or cut by wire EDMor 3D printed to create different horizontal expanded states such asoval, elliptical, circular, bean shaped, banana shaped or many otherpolygons and non-polygon shapes. The mean disc height at the L3-4 levelis 11.3 mm+/−1.8 mm, L4-5 11.3+/−2.1 mm and L5-S1 10.7+/−2.1 mm. Theaverage circumference of the L4 endplate is about 141 mm and surfacearea 1,492 mm² above. The device can have difference foot prints to tryto fill the endplate or disc space circumference. Referring now to FIGS.1A-1D, device 100 can include a device body 102. Generally, device body102 can be unitarily formed as a single monolithic construct, althoughmultiple component embodiments are also contemplated. Device body 102can include upper 104 a and lower 104 b bearing surfaces. As notedabove, device 100 can be inserted generally on its side such thatbearing surfaces 104 a, 104 b interface with and bear the forces of theadjacent vertebrae 10 (see FIGS. 4 and 5A-5B). In embodiments, thelarger threaded opening 126 are positioned dorsal or posterior and thesmaller opening 124 is positioned ventral or anterior. Device body 102can include a plurality of mediolateral body segments 106 unitaryconnected to each other by flexure 108 comprising a thin, flexible stripof material. As can be seen in, e.g., FIGS. 1C-1D, mediolateral bodysegments 106 and flexures 108 can perform a continuous, unitary outperimeter surface 110. Device body 102 can further include an anteriorbody segment 112 and posterior body segment 114. Anterior and posteriorbody segments 112, 114 can also be connected with mediolateral bodysegments by flexures 108. Device body 102 further defines an openinterior 116 between the body segments.

In the depicted embodiment, the device 100 includes three mediolateralbody segments 106 on each side such that the device includes a total ofeight body segments. In some embodiments, a device having eight bodysegments may be generally octagonally shaped in the expandedconfiguration as depicted in FIGS. 2A-2D. In other embodiments, devicemay have greater or fewer mediolateral body segments on each side.

Device body 102 can further include a plurality of locking flexures 118disposed in the open interior 116. As can be seen in, e.g., FIGS. 1C-1D,locking flexures 118 can extend from a lock base 120 that is recessedwith respect to bearing surfaces 104 a, 104 b. As will be described inmore detail below, each locking flexure 118 corresponds with lockingprojection 122 extending from an adjacent body segment 106.

Each of anterior body segment 112 and posterior body segment 114 caninclude a threaded opening that aids in insertion and expansion ofdevice. In one embodiment, anterior body segment 112 includes ananterior threaded opening 124 configured to interface with a stabilizingelement for inserting the device 100 into the disc space. Posterior bodysegment 114 can include a posterior threaded opening 126 that is largerthan anterior opening 124 and can be configured to interface with anexpansion element that is rotated to expand device body 112, which willbe described in more detail below. In other embodiments, anterioropening 124 may interface with the expansion elements while posterioropening 126 interfaces with the stabilizing element. In someembodiments, anterior body segment 112 can be tapered to facilitateinsertion of the device 100 into the disc space through the minimallyinvasive access opening.

FIGS. 2A-2D depict device 100 in an expanded configuration. As thedevice 100 is expanded, the mediolateral body segments 106 on opposingsides of the device body 102 are moved away from each other causing thedevice to expand medially and laterally within the disc space. When thedevice 100 is expanded, the locking flexures 118 interface and lock withthe locking projections 122 to prevent external forces from causes thedevice to compress from the expanded position following expansion. Ascan be seen in more detail in FIGS. 3A-3C, each locking flexure 118includes a pointed tip 128 that interfaces with a notch 130 in lockingprojections to lock the components together.

As noted above, in one embodiment device 100 is inserted betweenadjacent vertebrae 10 on its side, as shown in FIG. 4, with bearingsurfaces 104 a, 104 b configured to interface with the vertebrae. FIGS.5A-5B depict how the device 100 can be inserted in a collapsedconfiguration and then expanded within the disc space to occupy agreater footprint within the disc space. Note that these figures showone particular access approach and device orientation relative to thedisc space, but that other access approaches and device orientations arepossible. FIGS. 6A-6B depict device 100 with an insertion device 200used to insert and expand device 100 within the disc space according toan embodiment. As will be described in more detail below, insertiondevice 200 generally includes a stabilizing component 204 and anexpansion component 202. Expansion component 202 includes a knob 209configured to be rotated to secure the expansion component 202 tointervertebral device 100 and a dial 208 configured to be rotated toexpand intervertebral device 100, as discussed in more detail below.

Stabilizing component 204 includes a handle 206 configured to be rotatedto secure the component to device 100. FIGS. 7A-7E depict further detailregarding the components of insertion device 200.

Expansion component 202 includes a body 224, a shaft 222 extending fromthe body 224, a flange 226 at the distal end of shaft 222 and a distalthreaded tip 228. Shaft 222 and body 224 include internal lumens thatenable passage of shaft body 214 of stabilizing component 204 to passthrough expansion component 202. Distal tip 228 is sized to berotatingly received by posterior or proximal threaded opening 126 ofdevice. Flange 226 is wider than shaft 222 and threaded tip 228 toprevent expansion component 204 from being over-inserted when attachedto expandable device 100. Knob 209 and dial 208 are selectivelyattachable to expansion component 202 via, for example, a rotationalcoupling with knob 209 and with a screw 220 for dial 208. Dial 208 canalso include a threaded portion 221 configured to interface with aproximal threaded portion 212 of shaft 210. A lock 230 can beselectively insert into a lock aperture 232 through body 224 ofexpansion component 202 to lock rotation of stabilizing component 204with respect to expansion component 202, as will be discussed in moredetail below. Lock 230 can be selectively held in place with screw 234.

Stabilizing component 204 includes a shaft 210 extending from handle206. Shaft 210 includes a proximal threaded portion 212 configured tointerface with dial 208, a shaft body 214 configured to be extendedthrough the expansion component 202, an implant extension 216 configuredto extend through the implantable device 100 during implantation, and athreaded tip 218. Shaft 210 further includes a lock slot 236 configuredto interface with lock 230.

Lock 230 includes a handle 238 and a lock body 240. Lock body 240 isconfigured to be inserted through lock aperture 232 in body 224 ofstabilizing component 202. Lock body 240 further includes a recessedportion 242 having a reduced diameter that interfaces with the lock slot236 in shaft body 214 of shaft 210. Recessed portion 242 of lock body240 further includes a cutout 244 that allows for limited rotation ofshaft body 214 when lock 230 is engaged with shaft 210.

FIGS. 8A-8C further depict the interrelation of the components ofinserter 200. Dial 208 is threaded onto proximal threaded portion 212 ofstabilizing component 204. Shaft 210 of stabilizing component isinserted through expansion component 202 with implant extension 216 andthreaded tip 218 extending distally from expansion component 202.Proximal end of expansion component 202 is secured to dial 208 withscrew 220. Lock 230 can be selectively inserted into aperture 232 andthrough lock slot 236 in shaft 210.

FIGS. 9A-91 depict further details regarding the interaction betweeninserter 200 and expandable device 100. First, the distal tip 228 of theexpansion component 202 is engaged with the posterior threaded opening126 of implantable device 100 and the knob 209 is rotated to secure thetip 228 to the opening 126. If not already done so prior to attachingexpansion component 202, stabilizing component 204 is inserted throughstabilizing component 202 to the distal side of the expandable device100. The implant extension 216 can be extended through the body of theimplant 100 to engage the threaded tip 218 of the stabilizing component204 to interface with the distal threaded opening 124 of the implant.Handle 206 can be rotated to secure the tip 218 to the opening 124. Lock230 can now be inserted through slot 232 in expansion component andacross slot 236 in shaft 214 of stabilizing component.

The dial 208 of the expansion component 202 can now be rotated to expandthe implant 100 within the disc space. Dial 208 is rotated while theuser holds the knob 209 such that the dial rotates relative to knob 209.Lock 230 prevents shaft 214 from rotating such that stabilizingcomponent 204 maintains device 100 in a stable position. Dial 208therefore rotates shaft 222 and distal tip 228 about shaft 214 ofstabilizing component 204. This rotation pushes on the proximal oranterior end of device 100 while the distal or posterior end of thedevice is maintained stable, causing the distance between the anteriorand posterior ends of the device to shorten and the device 100 to expandlaterally outwardly. As described, above, device expands from thecollapsed configuration shown in, e.g., FIGS. 1A, 5A and 6A, to theexpanded configuration shown in, e.g., FIGS. 2A, 5B and 6B to cover awider footprint in the disc space. Implant is therefore able to providemore robust and stable support in the disc space that is laterally widerthan the access opening through which the implant is implanted.

As can be seen in FIGS. 9E-9H, the slot 236 in shaft 210 of stabilizingcomponent 204 can also serve to limit an amount that expansion component202 can be rotated to expand device 100. Referring to FIGS. 9E and 9G,initially the lock 230 is positioned in at a proximal end of slot 236.As the dial 208 is rotated to rotate the shaft 222 to expand the device100, the dial 208 travels linearly along the threaded portion 212 of thestabilizing component and the lock 230, which is inserted through alocking tube 231 of expansion component that enables shaft 222 to berotated, is advanced linearly along slot 236. In the fully expandedposition, as shown in FIG. 9H, the lock 230 abuts a distal end of theslot 236 such that further rotation of dial 208 with not cause anyfurther linear advancement of shaft 222. The length of the slot 236 canbe predetermined based on a desired or actual maximum expansion of theimplanted device 100.

Referring to FIG. 9I, the stabilizing component 204 can be removed byrotating handle 206 to disengage the threaded tip 218 from the deviceand withdrawing the shaft 210 from the expansion component 202. Thehollow expansion component 202 can then serve as a funnel to infuse oneor more of, for example, bone puddy, demineralized bone matrix, and bonechips into the now empty opening in the device 100 to aid the fusionprocess. Finally, the expansion component 202 can be disengaged from theimplant 100 and removed, leaving the implant in the disc space with,e.g., bone graft in the interior of the device 100.

The typical height opening after a discectomy available to insert theimplant can be from 4-14 mm depending on how collapsed the disc spaceis. One would need disc space distractors either a mechanical device ora lollipop sizer to expand the disc space. The typical width of thesurgical path into the disc space after retracting the nerve root couldbe 10-12 mm. Through a transforaminal interbody approach (TLIF:transforaminal interbody fusion) where you remove the superior andinferior facet you may be able to get an additional 1-2 mm more ofworking room.

In another embodiment, device can be inserted into the disc space andexpanded vertically to expand the disc space, with the flexures lockingthe device at the expanded height and maintaining the expanded discspace.

Various embodiments of systems, devices, and methods have been describedherein. These embodiments are given only by way of example and are notintended to limit the scope of the claimed inventions. It should beappreciated, moreover, that the various features of the embodiments thathave been described may be combined in various ways to produce numerousadditional embodiments. Moreover, while various materials, dimensions,shapes, configurations and locations, etc. have been described for usewith disclosed embodiments, others besides those disclosed may beutilized without exceeding the scope of the claimed inventions.

Persons of ordinary skill in the relevant arts will recognize that thesubject matter hereof may comprise fewer features than illustrated inany individual embodiment described above. The embodiments describedherein are not meant to be an exhaustive presentation of the ways inwhich the various features of the subject matter hereof may be combined.Accordingly, the embodiments are not mutually exclusive combinations offeatures; rather, the various embodiments can comprise a combination ofdifferent individual features selected from different individualembodiments, as understood by persons of ordinary skill in the art.Moreover, elements described with respect to one embodiment can beimplemented in other embodiments even when not described in suchembodiments unless otherwise noted.

Although a dependent claim may refer in the claims to a specificcombination with one or more other claims, other embodiments can alsoinclude a combination of the dependent claim with the subject matter ofeach other dependent claim or a combination of one or more features withother dependent or independent claims. Such combinations are proposedherein unless it is stated that a specific combination is not intended.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims, it is expressly intended thatthe provisions of 35 U.S.C. § 112(f) are not to be invoked unless thespecific terms “means for” or “step for” are recited in a claim.

1-20. (canceled)
 21. An expandable intervertebral body fusion device, comprising: a unitary monolithic body, the body having a plurality of body segments connected to each other with flexure members and an opening defined between the plurality of body segments, including— an anterior body segment and an opposing posterior body segment defining a maximum anterior to posterior width of the body; one or more mediolateral body segments extending between the anterior body segment and the posterior body segment along both a lateral side and a medial side of the anterior body segment and the posterior body segment, the one or more mediolateral body segments defining a maximum mediolateral width of the body; a threaded opening formed in at least one of the anterior body segment and the posterior body segment; and wherein the body is configured to be mediolaterally expanded from a compressed configuration to an expanded configuration by interaction of an expansion tool with the threaded opening causing the one or more mediolateral body segments on the lateral side and the one or more mediolateral body segments on the medial side to generally move away from each other and expand the opening between the plurality of body segments such that the body forms a greater mediolateral footprint in the expanded configuration than in the compressed configuration.
 22. The expandable intervertebral body fusion device of claim 21, wherein the threaded opening formed in at least one of the anterior body segment and the posterior body segment is configured to interface with an expansion element configured to be rotated to expand the body to the expanded configuration.
 23. The expandable intervertebral body fusion device of claim 21, wherein the threaded opening formed in at least one of the anterior body segment and the posterior body segment is configured to interface with a stabilizing element configured to stabilize the body when the body is expanded.
 24. The expandable intervertebral body fusion device of claim 1, wherein the body further comprises one or more locking flexures configured to lock the body in the expanded configuration.
 25. The expandable intervertebral body fusion device of claim 24, wherein there is at least one locking flexure extending from at least one mediolateral body segment on each of the lateral side and the medial side, and wherein each locking flexure is configured to interlock with an adjacent body segment.
 26. The expandable intervertebral body fusion device of claim 24, wherein each locking flexure comprises a flexible elongate body with a locking tip and is configured to interlock with a locking projection extending outwardly from an adjacent body segment.
 27. The expandable intervertebral body fusion device of claim 21, wherein there are three mediolateral body segments along each of the lateral side and the medial side.
 28. The expandable intervertebral body fusion device of claim 21, wherein in the expanded configuration the body has a generally polygonal shape.
 29. The expandable intervertebral body fusion device of claim 28, wherein in the expanded configuration the body has a generally octagonal shape.
 30. The expandable intervertebral body fusion device of claim 21, wherein in the expanded configuration the mediolateral footprint is approximately doubled in width from the compressed configuration.
 31. An expandable intervertebral body fusion device, comprising: a unitary monolithic body, the body having a plurality of body segments connected to each other with flexure members and an opening defined between the plurality of body segments, including— a first end body segment and an opposing second end body segment defining a maximum end to end width of the body; one or more side body segments extending between the first end body segment and the second end body segment along both a first side and a second side of the first end body segment and the second end body segment, the one or more mediolateral body segments defining a maximum side to side width of the body; a threaded opening formed in at least one of the first end body segment and the second end body segment; and wherein the body is configured to be expanded from a compressed configuration to an expanded configuration by interaction of an expansion tool with the threaded opening causing the one or more side body segments on the first side and the one or more side body segments on the second side to generally move away from each other and expand the opening between the plurality of body segments.
 32. The expandable intervertebral body fusion device of claim 31, where the body is expanded mediolaterally within the disc space such that the body forms a greater mediolateral footprint in the expanded configuration than in the compressed configuration.
 33. The expandable intervertebral body fusion device of claim 31, wherein the body is expanded transversely to the disc space to expand the disc space.
 34. The expandable intervertebral body fusion device of claim 33, wherein the body further comprises one or more locking flexures configured to lock the body in the expanded configuration to maintain the height of the expanded disc space against external forces.
 35. The expandable intervertebral body fusion device of claim 31, wherein the body further comprises one or more locking flexures configured to lock the body in the expanded configuration.
 36. The expandable intervertebral body fusion device of claim 35, wherein there is at least one locking flexure extending from at least one side body segment on each of the first side and the second side, and wherein each locking flexure is configured to interlock with an adjacent body segment.
 37. The expandable intervertebral body fusion device of claim 35, wherein each locking flexure comprises a flexible elongate body with a locking tip and is configured to interlock with a locking projection extending outwardly from an adjacent body segment.
 38. The expandable intervertebral body fusion device of claim 31, wherein there are three side body segments along each of the first side and the second side.
 39. The expandable intervertebral body fusion device of claim 31, wherein in the expanded configuration the body has a generally polygonal shape.
 40. The expandable intervertebral body fusion device of claim 39, wherein in the expanded configuration the body has a generally octagonal shape. 